1. Field of the Invention
This invention relates, in general, to means and methods for improved electronic devices, especially semiconductor devices and integrated circuits, and more particularly, to an improved manufacturing process for structures involving passivated metal layers or multiple passivated metal layers on nitride passivated substrates, and to structures, devices, and circuits made thereby.
2. Background Art
It is common practice in the manufacture of semiconductor devices and integrated circuits, and other electronic devices as well, to protect the semiconductor surface and the metal surface layers with a covering dielectric. This dielectric is referred to as the passivation layer or the metal passivation layer, and is often the outermost layer of the device. Openings are provided in the passivation layer through which external connections to the device may be made. As used herein, the word "device" is intended to include both individual devices, portions of devices, and collections of devices, as for example in integrated circuits and the like.
Frequently, a device will require multiple metal layers, one crossing over the other and separated by an interlayer dielectric. In this case the interlayer dielectric serves to passivate the first metal layer as well as insulate and separate it from the overlying second metal layer. Interlayer connection points are provided through openings formed for that purpose in the passivation layer serving as the interlayer dielectric.
With semiconductor and other devices having conductive substrates, a primary dielectric layer is also required between the substrate and any metal layers. This dielectric serves to passivate the substrate surface as well as insulate it from the metal layer or layers. Again, openings may be provided for connection points. When structures involving one or more metal layers superimposed on a dielectric layer and covered by a passivation layer are heated during subsequent manufacturing stages, as for example during assembly die bonding, it is found that voids frequently form in the metal layer or layers. These voids can be of appreciable size relative to the thickness and width of the metal conductor paths. The voids create weaknesses in the conductor paths which lead to reduced manufacturing yield and poorer reliability. This phenomenon is particularly severe when an aluminum alloy is used for the metal layer or layers and one of the several dielectric layers includes a nitride material. Thus, a need exists for a system of materials and manufacturing methods which reduces or eliminate the formation of voids in layered structures wherein one or more metal layers are sandwiched between dielectric layers. Because of their widespread use, there is a particular need for reducing or eliminating void formation in silicon oxide--nitride--aluminum alloy--doped oxide layer structures.
Accordingly, it is an object of this invention to provide an improved manufacturing method for the formation of metal--passivation layer structures wherein void formation in the metal layer is reduced or eliminated.
It is a further object of this invention to provide an improved manufacturing method for the formation of dielectric--first metal--first passivation--second metal--second passivation layer structures wherein void formation in one or both metal layers is reduced or eliminated.
It is an additional object of this invention to provide an improved process for the manufacture of dielectric--metal--passivation layer structures and/or dielectric--first metal--first passivation layer--second metal--second passivation layer structure, wherein the passivation layer or layers comprise a double layer.
It is a further object of this invention to provide the double layer by means of a first layer portion of a plasma formed oxide in contact with the underlying metal, and a second layer portion of a doped oxide overlying the first layer portion.
It is an additional object of this invention to provide the first layer portion by means of plasma enhanced chemical vapor deposition.
It is an additional object of this invention to provide the double layer by means of a first layer portion of an oxide which is in compressive stress and a second layer portion of an oxide which is not in compressive stress.
It is a further object of this invention to provide improved electronic devices made by the methods of this invention.